std::filesystem::space
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< cpp | filesystem
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Filesystem library
filesystem::space
Defined in header
<filesystem>
std::filesystem::space_info space( const std::filesystem::path & p );
(1)
(since C++17)
std::filesystem::space_info space( const std::filesystem::path & p,
std::error_code & ec ) noexcept;
(2)
(since C++17)
std::error_code & ec ) noexcept;
Determines the information about the filesystem on which the pathname p is located, as if by POSIX statvfs.
Populates and returns an object of type filesystem::space_info, set from the members of the POSIX struct statvfs as follows:
-
space_info.capacityis set as if by f_blocks * f_frsize. -
space_info.freeis set to f_bfree * f_frsize. -
space_info.availableis set to f_bavail * f_frsize. - Any member that could not be determined is set to static_cast<std::uintmax_t >(-1).
The non-throwing overload sets all members to static_cast<std::uintmax_t >(-1) on error.
[edit] Parameters
p
-
path to examine
ec
-
out-parameter for error reporting in the non-throwing overload
[edit] Return value
The filesystem information (a filesystem::space_info object).
[edit] Exceptions
Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.
1) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed with p as the first path argument and the OS error code as the error code argument.
2) Sets a std::error_code & parameter to the OS API error code if an OS API call fails, and executes ec.clear () if no errors occur.
[edit] Notes
space_info.available may be less than space_info.free.
[edit] Example
Run this code
#include <cstdint> #include <filesystem> #include <iostream> #include <locale> std::uintmax_t disk_usage_percent(const std::filesystem::space_info & si, bool is_privileged = false) noexcept { if (constexpr std::uintmax_t X(-1); si.capacity == 0 || si.free == 0 || si.available == 0 || si.capacity == X || si.free == X || si.available == X ) return 100; std::uintmax_t unused_space = si.free, capacity = si.capacity; if (!is_privileged) { const std::uintmax_t privileged_only_space = si.free - si.available; unused_space -= privileged_only_space; capacity -= privileged_only_space; } const std::uintmax_t used_space{capacity - unused_space}; return 100 * used_space / capacity; } void print_disk_space_info(auto const& dirs, int width = 14) { (std::cout << std::left ).imbue(std::locale ("en_US.UTF-8")); for (const auto s : {"Capacity", "Free", "Available", "Use%", "Dir"}) std::cout << "│ " << std::setw (width) << s << ' '; for (std::cout << '\n'; auto const& dir : dirs) { std::error_code ec; const std::filesystem::space_info si = std::filesystem::space(dir, ec); for (auto x : {si.capacity, si.free, si.available, disk_usage_percent(si)}) std::cout << "│ " << std::setw (width) << static_cast<std::intmax_t >(x) << ' '; std::cout << "│ " << dir << '\n'; } } int main() { const auto dirs = {"/dev/null", "/tmp", "/home", "/proc", "/null"}; print_disk_space_info(dirs); }
Possible output:
│ Capacity │ Free │ Available │ Use% │ Dir │ 84,417,331,200 │ 42,732,986,368 │ 40,156,028,928 │ 50 │ /dev/null │ 84,417,331,200 │ 42,732,986,368 │ 40,156,028,928 │ 50 │ /tmp │ -1 │ -1 │ -1 │ 100 │ /home │ 0 │ 0 │ 0 │ 100 │ /proc │ -1 │ -1 │ -1 │ 100 │ /null